The present invention relates to an agricultural harvester and in particular a harvester thresher, chopper or the like.
More particularly, it relates to an agricultural harvester with reversible drive system for a drawing-in device, provided with a switchable auxiliary drive with a hydraulic motor.
Agricultural harvesters of the above mentioned general type are known in the art. The drawing-in device in a harvester thresher includes for example a rotatably driven drawing-in screw extending transversely to the cutting direction, and an inclined conveyor passage located behind it in the throughflow direction of the harvested product and provided with a rotatably driven inclined conveyor for transporting the harvested product to a threshing mechanism. The drive is performed from a joint main drive through suitable laterally arranged driving elements, such as for example a belt drive.
It is known that the harvest must be carried out also in difficult conditions. Therefore, it is unavoidable that in the region of the drawing device compacting of the harvested product and clogging can occur. For this reason available agricultural harvesters are provided with reversible auxiliary drive for driving the circulating or rotatable elements during harvesting in opposite direction, when the main drive is uncoupled or turned off.
The European patent document 0180 027 B1 discloses an auxiliary drive device for reversing the drive of the drawing device of a harvester, provided with a hydraulic motor and a hydraulically switchable claw coupling. The coupling halves engage with one another for the reverse of the drive. This is carried out by a hydraulic switching valve and it is integrated in electrical-hydraulic circuit. The hydraulically actuatable coupling and the hydraulic motor are simultaneously supplied with pressurized oil. The pressure increase in the coupling for switching in the coupled condition is however obtained before the required pressure for driving the hydraulic motor is adjusted. Thereby it must be guaranteed that the coupling is coupled before the hydraulic motor performs its operating functions.
The above described auxiliary drive device is structurally extremely complicated and therefore very cost intensive. It must include the coupling, the switching valve, the plurality of hydraulic conduits and the electrical wiring. Therefore it is disturbance prone in rough conditions which occur during harvesting.